Horton

Re: Add SPLIT PARTITION/MERGE PARTITIONS commands

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: Dmitry Koval <d.koval@postgrespro.ru>
Cc: Alexander Korotkov <aekorotkov@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2025-08-22T03:36:45Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Adjust errcode in checkPartition()

  2. Fix usage of palloc() in MERGE/SPLIT PARTITION(s) code

  3. Implement ALTER TABLE ... SPLIT PARTITION ... command

  4. Implement ALTER TABLE ... MERGE PARTITIONS ... command

  5. Calculate agglevelsup correctly when Aggref contains a CTE.

  6. Use PqMsg_* macros in applyparallelworker.c.

  7. Restrict psql meta-commands in plain-text dumps.

  8. Ensure we have a snapshot when updating various system catalogs.

  9. Use specific collation where needed in new test

  10. Expand virtual generated columns in the planner

  11. Virtual generated columns

  12. Define PG_LOGICAL_DIR for path pg_logical/ in data folder

  13. Revert support for ALTER TABLE ... MERGE/SPLIT PARTITION(S) commands

  14. Avoid repeated table name lookups in createPartitionTable()

  15. Provide deterministic order for catalog queries in partition_split.sql

  16. Don't copy extended statistics during MERGE/SPLIT partition operations

  17. Fix the name collision detection in MERGE/SPLIT partition operations

  18. Fix regression tests conflict in 3ca43dbbb6

  19. Add permission check for MERGE/SPLIT partition operations

  20. Fix one more portability shortcoming in new test_pg_dump test.

  21. Inherit parent's AM for partition MERGE/SPLIT operations

  22. Add tab completion for partition MERGE/SPLIT operations

  23. Rename tables in tests of partition MERGE/SPLIT operations

  24. Make new partitions with parent's persistence during MERGE/SPLIT

  25. Document the way partition MERGE/SPLIT operations create new partitions

  26. Change the way ATExecMergePartitions() handles the name collision

  27. Grammar fixes for split/merge partitions code

  28. Checks for ALTER TABLE ... SPLIT/MERGE PARTITIONS ... commands

  29. Fix some grammer errors from error messages and codes comments

  30. Support TZ and OF format codes in to_timestamp().

  31. Support identity columns in partitioned tables

  32. Fix indentation in twophase.c

  33. Fix corner-case planner failure for MERGE.

  34. Doc: fix documentation example for bytea hex output format.

  35. Avoid repeated name lookups during table and index DDL.

Attachments

On Thu, Aug 21, 2025 at 2:45 PM jian he <jian.universality@gmail.com> wrote:
>
> On Thu, Aug 21, 2025 at 10:53 AM jian he <jian.universality@gmail.com> wrote:
> >
> > > this time, I only checked
> > > v52-0001-Implement-ALTER-TABLE-.-MERGE-PARTITIONS-.-comma.patch

hi.

+static void
+check_two_partitions_bounds_range(Relation parent,
+{
....
+
+ ereport(ERROR,
+ errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+ errmsg("lower bound of partition \"%s\" is not equal to the upper
bound of partition \"%s\"",
+   second_name->relname, first_name->relname),
+ errhint("ALTER TABLE ... MERGE PARTITIONS requires the partition
bounds to be adjacent."),
+ parser_errposition(pstate, datum->location));
+ }

I propose change it to:
        ereport(ERROR,
                errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                errmsg("can not merge partition \"%s\" together with
partition \"%s\"",
                       second_name->relname, first_name->relname),
                errdetail("lower bound of partition \"%s\" is not
equal to the upper bound of partition \"%s\"",
                          second_name->relname, first_name->relname),
                errhint("ALTER TABLE ... MERGE PARTITIONS requires the
partition bounds to be adjacent."),
                parser_errposition(pstate, datum->location));


    <para>
+     There is also an option for merging multiple table partitions into
+     a single partition using the
+     <link linkend="sql-altertable-merge-partitions"><command>ALTER
TABLE ... MERGE PARTITIONS</command></link>.
+     This feature simplifies the management of partitioned tables by allowing
+     users to combine partitions that are no longer needed as
+     separate entities.  It's important to note that this operation is not
+     supported for hash-partitioned tables and acquires an
+     <literal>ACCESS EXCLUSIVE</literal> lock, which could impact high-load
+     systems due to the lock's restrictive nature.  For example, we can
+     merge three monthly partitions into one quarter partition:
I am not sure last sentence "merge three monthly partitions into one
quarter partition:"
is correct.


buildExpressionExecutionStates seems not needed, same reason as
mentioned before,
code pattern aligned with ATRewriteTable.
while at it, also did some minor changes.